Trimming Your Rabbit's Toenails
It is important to trim your rabbit's nails regularly to avoid discomfort to the rabbit should the nails grow too long. It will also help protect you from sharp claws should the rabbit scratch you.
There are a variety of different toenail clippers that you can use for your rabbit. The most common ones are pictured below.

When trimming the toenails, you can either have the rabbit on it's back in your lap, or the rabbit sitting down on the floor or table. Whichever way is the most comfortable for both you and the rabbit is the method you should use.
When trimming it is easiest to do one paw at a time so you do not accidentally skip any nails. There are 5 claws on each front paw, including the dewclaw on the inside, and 4 claws on each back paw. Make sure to not cut past the 'quick' of the nail, which is the blood vessel that extends part way down the nail. It is especially difficult to see in dark toenails. For this reason, it is best to have good lighting when you are trimming the nails to ensure you do not cut into this blood vessel. The photo below shows where the vessel is and where you should cut on the nail.

If you should cut into the blood vessel, use styptic powder to help stop the bleeding. If you do not have any on hand, you can use a paper towel to absorb the blood until it stops bleeding on its own.